The present invention relates to impregnation treatment of meat, particularly pork, and to impregnation of pork with an aqueous medium, such as a solution medium containing brine salt and/or a curing agent, with or without a solubilizing agent and/or a cure accelerator, and/or other food and food-acceptable substances, and in particular, the present invention relates to utilization of pale, soft and exudative pork.
In view of changing consumer attitudes and preferences over the past thirty-some years, pork producers have bred and fed pigs to reduce fat content and increase lean meat yield. As reported by Wirth, in his article "The Technology of Processing Meat Not of Standard Quality", Fleischwirtsch, 66 (8), 1986, pp. 1255-60, the lean meat:fat ratio of pigs has been altered over the years from about 1:1 to about 2:1. However, as also reported by Wirth, increased yield of lean meat has been achieved at the expense of quality since, as is accepted in the art, a significant percentage of lean-bred pigs, when alive, react adversely to stress, including stress induced by pre-slaughter procedures, which produces effects deleterious to the post-mortem meat. In fact, as reported by Topel, et al., "Porcine Stress Syndrome", Mod. Vet. Proct. 49:40, 1968, the stress not only may affect the quality of the meat, but also may lead to sudden death.
One result of porcine stress syndrome is a rapid post-mortem glycolysis reaction in muscle tissue which effects production and accumulation of lactic acid in the muscle tissue and which effects protein denaturation and cellular damage. Such pork is whitish, or pale, in color, and in an uncooked condition, it has a soft, dry and mushy texture. These characteristics have lent the meat to be characterized in the pork industry and in the art as pale, soft and exudative pork (hereinafter "PSE" pork). PSE pork has what is considered in the pork industry and characterized in the art as poor functionality, including poor water-binding/retention characteristics and poor cure-color characteristics.
One objective indicium for identifying what is characterized in the pork industry and in the art as PSE pork is that in less than 1 hr post-mortem, a glycolysis reaction produces lactic acid which effects a significant drop in the pH of the meat. In general, within that time period, the pH of the meat drops to at least less than about 5.8, and generally, PSE pork will acquire a pH of about 5.3 to about 5.4 within about 3 hrs post-mortem. It is also not uncommon for PSE pork to acquire a pH of less than about 5.3 upon complete rigor mortis. In addition, PSE pork may be identified because of the denaturation of proteins, which include denaturation of creatine kinase and, in particular, myosin and actomyosin, the denaturation occurring particularly during the first hour post-mortem. (Cf., Penny, Protein denaturation and water-holding capacity in pork muscle, J.Fd. Technol. (1969) 4, 269-273).
In comparison, post-mortem glycolysis in what is considered as "normal", and hence desirable, pork results in a pH drop which is much more gradual and thus, not particularly detrimental to proteins and to cellular structure, in that the pH drops only to about 5.9 to about 6 in about 1 hr to about 3 hrs post-mortem. Moreover, upon complete rigor mortis, i.e., within about 8 hrs to about 12 hrs, normal pork has a pH above about 5.3, and generally from about 5.4 to about 5.8 and more particularly about 5.5 to about 5.8.
Because the extent of protein denaturation and cellular damage post-slaughter are primary variables which affect the texture and meat fluid-/water binding/ holding/retention capacity (hereinafter solely "water-holding" capacity) of pork products, normal pork sets the standard for the water-holding capacity and texture which consumers have come to expect and prefer and which is therefore sought as a standard in the pork industry. That, therefore, likewise sets the standard of high-quality, high value use and hence, the price standard for the commodity.
Also in comparison, a third classification of pork is known as dark, firm and dry pork (hereinafter "DFD" pork). DFD pork has physio-chemical characteristics which, on a linear scale, oppose those of PSE pork, e.g., dark versus light color and good versus poor water-holding capacity characteristics, these characteristics being a result of post-mortem pork experiencing even less glycolosis than does normal pork. Upon completion of rigor mortis, DFD pork has a pH of above 6 and generally from about 6.2 to about 7.
A further indicium of identifying PSE pork is the genetic make-up of the pig based upon determination of the character of its halothane genes. In general, about 80% of the pig population has two recessive halothane genes, and these pigs are not particularly susceptible to porcine stress syndrome. However, if these pigs are subjects of unusual pre-slaughter environmental activity, they may stress sufficiently such that, all or part of their post-mortem meat may exhibit PSE characteristics.
On the other hand, approximately 1% of pigs have two dominant, i.e., homozygous, halothane genes, and about 100% of these pigs provide meat which is characterized post-mortem as PSE pork. In addition, about 15-20% of the pig population have heterozygous halothane genes, i.e., one dominant and one recessive gene, and when these pigs are subjected to the usual stress in conventional large-scale slaughtering processes, their meat, too, in general, will be characterized post-slaughter as PSE pork.
Thus, in general, up to about 20%, if not more, of the pig population is particularly susceptible to the effects of porcine stress syndrome which contributes to production of pork characterized post-slaughter as PSE pork. Also, however, in general, although the meat of an entire individual pig may be identified post-slaughter as PSE pork, it is found, such as with pigs having recessive halothane genes, as referred to above, or with pigs having heterozygous halothane genes, that not all cuts of any particular pig necessarily will have PSE characteristics.
Therefore, in commercial packing facilities, whereat, in general, post-mortem meat is butchered into loin, ham and bacon cuts, i.e., respectively, the part of the sides between the shoulder and pelvis (loin), the thigh, hind leg and buttocks (ham), and belly, and remainder of the back and sides (bacon), the characteristics of each cut may be evaluated separately. Thus, particular cuts of an individual pig may be identified as being PSE pork, although other cuts of the same pig may not, and these differing cuts generally are segregated during processing. In general, for any particular pig, the ham cut will be found to be most susceptible to development of PSE characteristics.
Although it is known that PSE pork takes up sodium chloride and other salts well because of its low pH, brine-cured PSE pork cuts present problems because of their poor water-holding characteristics, which are not offset by water-holding properties effected somewhat by salts. Also because of their poor water-holding characteristics, cooking PSE pork cuts for sale or consumption results in undesirable fluid losses, and hence, yield losses, which further contribute to an undesirable texture and mouth-feel. Thus, PSE pork cuts have been considered unsuitable for providing cured or cooked, or cured and cooked, or fried and/or smoked products, because of fluid losses experienced during cooking, frying and/or smoking, since the meat acquires a soft, dry and pithy texture during such processing, which is in contradistinction to a mouth-feel and bite consumers have come to expect from a quality high-value meat. Moreover, because of lactic acid accumulation, PSE pork also may be perceived as having acidic, i.e., sour, notes which further may detract from organoleptic appeal.
In addition, exudate/drip from PSE pork cuts when packaged, particularly if such have been impregnated with brine and/or curing solutions, also presents an unappealing appearance to consumers. Furthermore, the poor water-holding capacity of PSE pork cuts inhibit their usefulness in ready-to-eat, pre-cooked and chilled products and in sliced products. Usefulness of PSE pork is also inhibited significantly in other so-called convenience foods, such as microwaveable products precooked products which require significant industrial processing prior to shipment for wholesale or retail sale.
PSE pork, therefore, generally is considered a less than preferable and low-value product, and when it is sold itself as a cut, it is marketed generally as a non-label or off-label product. Thus, to enhance its value and usefulness, it has been proposed that it may be possible to use PSE pork for products wherein fluid loss is not of concern or wherein fluid loss is intended, i.e., dehydrated meat products. It is also possible to particulate the product and mix and preferably, emulsify it with other particulated meat products or by-products and/or with fillers and extenders to make luncheon meat-type products, such as bologna-type products, wherein a soft texture is not undesirable.
To address the problems posed by PSE pork, in addition to resting pigs prior to slaughter, which generally is not practical in a large-scale commercial setting, it has been proposed that the meat be rapidly chilled immediately after slaughter to inhibit the conversion of glycogen to lactic acid and substantially avoid protein denaturation. That, however, as will be appreciated, involves not only a large investment in equipment, but also would involve treating pork which is not subject to the PSE problems. Moreover, it is not necessarily desirable to so treat all meats, and procedures have not yet even been proposed to enable identification of PSE meat prior to or immediately after slaughter, which would be required if PSE/non-PSE portions of individual pigs are to be segregated immediately and subjected to a post-mortem treatment.
A further proposal to address the problems, which is much more practical and applicable to treatment of all meat without discrimination, has been advanced by Knipe, etal., "Effects of Stress-Susceptibility of Hogs and Processing Treatments on the Quality of Pork Products", Proc. Int. Congress of Meat and Sci. and Tech. Vol. 2, p. 662, 1990, wherein studies demonstrated that a quality improvement was effected by injecting prerigor pork with a curing pickle brine containing sodium tripoly-hexametaphosphate.
However, PSE pork, which constitutes a significant percentage of slaughtered pork products, has been considered a problematic product and caused significant monetary losses in the industry. Thus, further means to address and alleviate the problems long have been desired and sought together with, alternatively, means to obtain more economic value from PSE pork than is provided by the uses noted above.